Experiments-Learn about Oxidation

Let's investigate!

Why does fruit turn brown when you cut it?

An experiment with citric acid that teaches about oxidation

What is Oxidation?

Well, it is pretty much the process of making things rusty. We're going to show you how to do an oxidation experiment.

You see, oxidation (say: ahk-sih-day-shun), can happen outside in your yard with an iron nail and a lot of rain. I'm sure you know what I'm tallking about. You've all seen a rusty nail. You may even have a bigger brother or sister that drives around in a rusty old car.

Well, we are not going to talk about oxidized car parts. After all, this is a cooking club, not a body shop! Oxidation also happens with food too. You can most easily see it happen to things like pears, apples, potatoes, and bananas. So that is how we plan to do our oxidation experiment.

You see these kinds of foods have an enzyme (say: en-ziy-m) in them that reacts with the air. You know what an enzyme is, right? Apples and other produce like pears, bananas, and potatoes have an enzyme called: polyphenol oxidase (say:  pawl-ee-fee-nole ah-xs-ah-daze) that reacts with the oxygen (say: ah-xs-ee-gen) in our air and the phenols in our foods. This process is called oxidation!  Phenols have iron in them (so this is what makes them turn rusty looking, and they are also yummy treats for yeast to feed off of.

Psst-- Hot Fact!If you grow a fungus and a bacteria together in a pile of sawdust they will make so much heat the sawdust will catch fire! If you remember our first experiment with yeast and sugar, then you understand why spoiled, brown fruit flesh is not healthy to eat. This reaction basically forms a sort of rust color on the fruit. You get brown fruit a few minutes after you bite into it or cut it because doing these things will damage the cells in the fruit. If you take a bite and leave it on the table, then you give the fruit time to oxidize and turn brown. Now they are ready for fungus to grow on them because fungus loves brown, rusty looking, oxidized fruits and vegetables!

In today's experiment, we are going to see what we can do to slow down or stop the oxidation of our pear.

Our oxidation experiment will need special equipment:

Want more? Download these Oxidation Experiment Sheets!

For kids ages 5-7	For kids ages 8-11